What are the precautions I need to follow before deleting my WINDOWS OS and keeping only UBUNTU?

So I have been using Ubuntu for a long time and I hardly use windows anymore. I have decided to remove windows OS and keep only ubuntu. My laptop specs are 1TB memory 8gb RAM i-5 7th gen. 4 cores.

I had only alloted 100GB for my UBUNTU and rest 900GB is for windows. Where c drive is 351 gb, D drive is 441 gb and some lenovo drives that add up to around 50gb. I have copied all my important files into a hard disk.

When I remove my windows does my system automatically allot the 900gb to ubuntu? I am not concerned with my data in windows. But I want to know what precautions I need to take before deleting windows.